The Afghan-born make-up artist put an end to rumors swirling that Cowell, 50, was about to pop the question when she made the announcement to RadarOnline.com last week.

The couple, who met on the set of the hit FOX competition program, reportedly began dating a year ago.

Celebrity jeweler David Mamane was impressed with Cowell's choice of jewelry, telling UsMagazine.com, "I never would have pegged Simon Cowell to be a guy that spends so much money on a woman. But he sure did well!"

Mamane estimates the brilliant cut bauble to be "approximately six carats and an estimated $750,000."

"You can see that the clarity and color is nothing less than perfect!" he added.

Cowell's mother, Julie, has also voiced her approval for her son and future daughter-in-law.

Telling the U.K.'s The Mirror that she's very "excited" for their upcoming nuptials, Julie added that she hopes the couple decides to tie the knot at her neighboring chuch, St. Margarets in the town of Rottingdean.

"I've told Simon [that] Father Martin Morgan would be very happy if he got married there as we have a long history with the church," she said. "Simon is very committed for the first time ever which is wonderful. The wedding is very important to me."